Sequence for reference signals during beam refinement

ABSTRACT

Methods, systems, and devices for wireless communication are described. Wireless communications systems may support beamformed transmissions between devices (e.g., to improve coverage range). The beamformed transmissions may depend on discovery and maintenance of receive and transmit beams over which a given device may communicate with another device. Various receive and transmit beams for a given device may be compared using reference signals. As the number of devices attempting to access a cell increases, the number of reference signals to be transmitted may scale proportionally. Large numbers of reference signals may flood time-frequency resources of the system and/or require excessive processing at a mobile device. Scrambling sequences for reference signals may be employed to improve efficiency of resource usage. In aspects, the scrambling sequences may be implicitly determined (e.g., based on resources over which the access request was transmitted). Such an implicit association may reduce the need for additional signaling.

CROSS REFERENCES

The present application for patent is a continuation of U.S. patentapplication Ser. No. 15/963,785 by Nagaraja et al., entitled “SequenceFor Reference Signals During Beam Refinement” filed Apr. 26, 2018, whichclaims priority to U.S. Provisional Patent Application No. 62/501,619 byNagaraja et al., entitled “Sequence For Reference Signals During BeamRefinement,” filed May 4, 2017, which is assigned to the assignee hereofand expressly incorporated by reference herein in its entirety.

BACKGROUND

The following relates generally to wireless communication and, morespecifically, to sequences for reference signals during beam refinement.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, and orthogonal frequencydivision multiple access (OFDMA) systems, (e.g., a Long Term Evolution(LTE) system, or a New Radio (NR) system). A wireless multiple-accesscommunications system may include a number of base stations or accessnetwork nodes, each simultaneously supporting communication for multiplecommunication devices, which may be otherwise known as user equipment(UE).

In some wireless communications systems (e.g., systems supportingmillimeter wave (mmW) communications), beamforming may be used in orderto overcome the relatively high path losses associated with frequenciesin these systems. In order to support beamformed transmissions,communicating wireless devices (e.g., a base station, UE, etc.) may beoperable to discover and maintain suitable beams for a givencommunication link. The set of procedures and protocols required forthis task may be referred to as beam refinement. As an example, beamrefinement may be based on a UE observing beamformed downlink referencesignals from a base station and reporting one or more performancemetrics for the respective beamformed reference signals back to the basestation. In some cases, multiple UEs may attempt to access a cellassociated with a given base station at the same time (or nearly thesame time). The base station may accordingly transmit reference signalsto enable beam refinement for multiple UEs. The number of referencesignals may scale proportionally to the number of UEs, resulting inmeasurement overhead for the UEs or signaling overhead for the wirelesscommunications system as a whole. Improved techniques for referencesignal management during beam refinement may be desired.

SUMMARY

The described techniques relate to improved methods, systems, devices,or apparatuses that support scrambling sequences for reference signalsduring beam refinement. In some aspects, one or more user equipments(UEs) may attempt to access a cell of a base station (e.g., using arandom access procedure) within a given time period. Each UE maytransmit an access request over a set of resources (e.g., time-frequencyresources, preamble resources, etc.) corresponding to a detectedsynchronization signal of the cell. Upon detecting access requests fromthe one or more UEs, the base station may transmit downlink beamreference signals that are scrambled in a predictable manner. Thescrambled downlink beam reference signals may accompany a random accessresponse, which is transmitted within a random access response windowcorresponding to the access requests from the UEs. Alternatively, thescrambled downlink beam reference signals may precede or come after therandom access response within the random access response window. In somecases, the scrambling sequences for the downlink beam reference signalsmay be based on the resources over which the access request wastransmitted. Accordingly, in the case that reference signals formultiple UEs are transmitted over the same resources or over resourceswhich are tied to a common control region, a given UE may infer whichreference signals are intended for it by mapping the resources overwhich the access request was transmitted to one or more potentialscrambling sequences. Similarly, on the uplink (and in response to therandom access response), the UE may transmit one or more scrambledreference signals (e.g., which may be scrambled using the samescrambling sequences as the downlink reference signals or usingscrambling sequences from a different set of potential sequences) to thebase station. These uplink reference signals may be accompanied by areport in which the UE conveys one or more preferred downlink transmitbeams. Based on the uplink and downlink reference signals, the UE andbase station may select uplink and downlink beam pairs for subsequentcommunications.

A method of wireless communication is described. The method may includereceiving a first random access message from a first UE over a first setof resources; transmitting, in a first transmission time interval inresponse to the first random access message, one or more downlink beamreference signals scrambled with respective downlink scramblingsequences of a set of downlink scrambling sequences, the set of downlinkscrambling sequences selected from a plurality of sets of downlinkscrambling sequences based on the first set of resources; and receivingfirst channel feedback information from the first UE, where the firstchannel feedback information is based on measurements of the downlinkbeam reference signals.

An apparatus for wireless communication is described. The apparatus mayinclude means for receiving a first random access message from a firstUE over a first set of resources; means for transmitting, in a firsttransmission time interval in response to the first random accessmessage, one or more downlink beam reference signals scrambled withrespective downlink scrambling sequences of a set of downlink scramblingsequences, the set of downlink scrambling sequences selected from aplurality of sets of downlink scrambling sequences based on the firstset of resources; and means for receiving first channel feedbackinformation from the first UE, where the first channel feedbackinformation is based on measurements of the downlink beam referencesignals.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to receive a first random accessmessage from a first UE over a first set of resources; transmit, in afirst transmission time interval in response to the first random accessmessage, one or more downlink beam reference signals scrambled withrespective downlink scrambling sequences of a set of downlink scramblingsequences, the set of downlink scrambling sequences selected from aplurality of sets of downlink scrambling sequences based on the firstset of resources; and receive first channel feedback information fromthe first UE, where the first channel feedback information is based onmeasurements of the downlink beam reference signals.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to receive a first randomaccess message from a first UE over a first set of resources; transmit,in a first transmission time interval in response to the first randomaccess message, one or more downlink beam reference signals scrambledwith respective downlink scrambling sequences of a set of downlinkscrambling sequences, the set of downlink scrambling sequences selectedfrom a plurality of sets of downlink scrambling sequences based on thefirst set of resources; and receive first channel feedback informationfrom the first UE, where the first channel feedback information is basedon measurements of the downlink beam reference signals.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for sending one or more transmissionsto the first UE via a downlink transmit beam selected based on the firstchannel feedback information.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying, from a plurality ofsets of uplink scrambling sequences, a set of uplink scramblingsequences for one or more uplink beam reference signals. Some examplesof the method, apparatus, and non-transitory computer-readable mediumdescribed above may further include processes, features, means, orinstructions for receiving the one or more uplink beam reference signalsscrambled with respective ones of the set of uplink scramblingsequences.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the set of uplink scramblingsequences may be identified based on the first set of resources, anindicator transmitted in a random access response to the first randomaccess message, a second indicator transmitted in a handover command, orsome combination thereof.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a second random accessmessage from a second UE over a second set of resources. Some examplesof the method, apparatus, and non-transitory computer-readable mediumdescribed above may further include processes, features, means, orinstructions for transmitting, in the first transmission time intervalin response to the second random access message, one or more seconddownlink beam reference signals scrambled with respective downlinkscrambling sequences of a second set of downlink scrambling sequences,the second set of downlink scrambling sequences selected from theplurality of sets of downlink scrambling sequences based on the secondset of resources. Some examples of the method, apparatus, andnon-transitory computer-readable medium described above may furtherinclude processes, features, means, or instructions for receiving secondchannel feedback information from the second UE, where the secondchannel feedback information may be based on measurements of the seconddownlink beam reference signals.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for transmitting, in a secondtransmission time interval, a random access response to the first andsecond UEs, the random access response including respective grants ofuplink resources for the first and second channel feedback information.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the random access response maybe transmitted within a first response window after the reception of thefirst random access message and within a second response window afterthe reception of the second random access message.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for indicating, in a downlink controlinformation transmission, a first transmission time interval for thetransmitting of the one or more downlink beam reference signals and theone or more second downlink beam reference signals.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the first transmission timeinterval may be prior to the second transmission time interval orsubsequent to the second transmission time interval.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the first transmission timeinterval and the second transmission time interval may be a sametransmission time interval.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the random access responseincludes an indicator of a third transmission time interval fortransmission of uplink beam reference signals from the first UE. In someexamples of the method, apparatus, and non-transitory computer-readablemedium described above, a second indicator of a fourth transmission timeinterval for transmission of second uplink beam reference signals fromthe second UE.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the first set of resourcesincludes time resources, frequency resources, preamble resources, or acombination thereof.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying time and frequencyresources for the one or more downlink beam reference signals based onthe first set of resources.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a second random accessmessage from a second UE over the first set of resources. Some examplesof the method, apparatus, and non-transitory computer-readable mediumdescribed above may further include processes, features, means, orinstructions for receiving second channel feedback information from thesecond UE, where the second channel feedback information may be based onmeasurements of the downlink beam reference signals.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving a data message from thefirst UE based on the first random access message, where the set ofdownlink scrambling sequences are determined based on information withinthe data message.

A method of wireless communication is described. The method may includeidentifying a downlink transmit beam of a plurality of downlink transmitbeams for synchronization signals transmitted by a base station;transmitting a random access message using a first set of resources, thefirst set of resources being selected based on the identified downlinktransmit beam; receiving, in response to the random access message, oneor more downlink beam reference signals scrambled with respectivedownlink scrambling sequences of a set of downlink scrambling sequences,the set of downlink scrambling sequences selected from a plurality ofsets of downlink scrambling sequences based on the first set ofresources; and transmitting channel feedback information based onmeasurements of the downlink beam reference signals.

An apparatus for wireless communication is described. The apparatus mayinclude means for identifying a downlink transmit beam of a plurality ofdownlink transmit beams for synchronization signals transmitted by abase station; means for transmitting a random access message using afirst set of resources, the first set of resources being selected basedon the identified downlink transmit beam; means for receiving, inresponse to the random access message, one or more downlink beamreference signals scrambled with respective downlink scramblingsequences of a set of downlink scrambling sequences, the set of downlinkscrambling sequences selected from a plurality of sets of downlinkscrambling sequences based on the first set of resources; and means fortransmitting channel feedback information based on measurements of thedownlink beam reference signals.

Another apparatus for wireless communication is described. The apparatusmay include a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe operable to cause the processor to identify a downlink transmit beamof a plurality of downlink transmit beams for synchronization signalstransmitted by a base station; transmit a random access message using afirst set of resources, the first set of resources being selected basedon the identified downlink transmit beam; receive, in response to therandom access message, one or more downlink beam reference signalsscrambled with respective downlink scrambling sequences of a set ofdownlink scrambling sequences, the set of downlink scrambling sequencesselected from a plurality of sets of downlink scrambling sequences basedon the first set of resources; and transmit channel feedback informationbased on measurements of the downlink beam reference signals.

A non-transitory computer readable medium for wireless communication isdescribed. The non-transitory computer-readable medium may includeinstructions operable to cause a processor to identify a downlinktransmit beam of a plurality of downlink transmit beams forsynchronization signals transmitted by a base station; transmit a randomaccess message using a first set of resources, the first set ofresources being selected based on the identified downlink transmit beam;receive, in response to the random access message, one or more downlinkbeam reference signals scrambled with respective downlink scramblingsequences of a set of downlink scrambling sequences, the set of downlinkscrambling sequences selected from a plurality of sets of downlinkscrambling sequences based on the first set of resources; and transmitchannel feedback information based on measurements of the downlink beamreference signals.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving one or more transmissionsfrom the base station via a downlink beam pair including a downlinktransmit beam and a downlink receive beam, the downlink beam pairselected based on the channel feedback information.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying a set of uplinkscrambling sequences for one or more uplink beam reference signals froma plurality of sets of uplink scrambling sequences. Some examples of themethod, apparatus, and non-transitory computer-readable medium describedabove may further include processes, features, means, or instructionsfor transmitting the one or more uplink beam reference signals scrambledwith respective ones of the set of uplink scrambling sequences.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the set of uplink scramblingsequences may be identified based on the first set of resources, anindicator transmitted in a random access response to the first randomaccess message, a second indicator transmitted in a handover command, orsome combination thereof.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for receiving, in a first transmissiontime interval, a random access response to the random access message,the random access response including a grant of uplink resources for thechannel feedback information.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the random access response maybe received within a response window after the transmission of therandom access message.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying a second transmissiontime interval for the receiving of the one or more downlink beamreference signals based on a downlink control information transmission.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the second transmission timeinterval may be prior to the first transmission time interval orsubsequent to the first transmission time interval.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the second transmission timeinterval and the first transmission time interval may be a sametransmission time interval.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the random access responseincludes an indicator of a second transmission time interval fortransmission of uplink beam reference signals.

In some examples of the method, apparatus, and non-transitorycomputer-readable medium described above, the first set of resourcesincludes time resources, frequency resources, preamble resources, or acombination thereof.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying time and frequencyresources for the one or more downlink beam reference signals based onthe first set of resources.

Some examples of the method, apparatus, and non-transitorycomputer-readable medium described above may further include processes,features, means, or instructions for identifying a downlink transmitbeam of a plurality of downlink transmit beams for synchronizationsignals transmitted by a base station. Some examples of the method,apparatus, and non-transitory computer-readable medium described abovemay further include processes, features, means, or instructions forselecting the first set of resources based on the identified downlinktransmit beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system for wireless communicationthat supports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a wireless communications system thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIG. 3A illustrates an example of a synchronization transmission thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIG. 3B illustrates an example of an access channel configuration thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIG. 4 illustrates an example of a random access response configurationthat supports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example of an access report configuration thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIG. 6 illustrates an example of a process flow that supports scramblingsequences for reference signals during beam refinement in accordancewith aspects of the present disclosure.

FIGS. 7 through 9 show block diagrams of a device that supportsscrambling sequences for reference signals during beam refinement inaccordance with aspects of the present disclosure.

FIG. 10 illustrates a block diagram of a system including a base stationthat supports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.

FIGS. 11 through 13 show block diagrams of a device that supportsscrambling sequences for reference signals during beam refinement inaccordance with aspects of the present disclosure.

FIG. 14 illustrates a block diagram of a system including a userequipment (UE) that supports scrambling sequences for reference signalsduring beam refinement in accordance with aspects of the presentdisclosure.

FIGS. 15 through 16 illustrate methods for scrambling sequences forreference signals during beam refinement in accordance with aspects ofthe present disclosure.

DETAILED DESCRIPTION

In some wireless communications systems, beamforming is used to overcomepath loss associated with operational frequencies of these wirelesssystems. However, beamforming may generally be used in any scenario inwhich improved cellular coverage is desired. In order to supportbeamformed transmissions, communicating devices may perform beamdiscovery and refinement in which multiple transmit or receive beamcandidates are evaluated. In order to evaluate the multiple transmit orreceive beams, reference signals may be employed. For example, a basestation may transmit multiple reference signals, where each referencesignal corresponds to a respective downlink transmit beam. A userequipment (UE) may attempt to receive each reference signal over one ormore downlink receive beams. A suitable beam pair (e.g., comprising adownlink transmit beam and a downlink receive beam) may be selectedbased on one or more reference signal measurements performed at the UE.Subsequent communications may benefit from the use of the selected beampair. Analogous beam refinement may be performed for uplinktransmissions as well.

However, when multiple UEs attempt to access a cell of a base stationwithin a relatively short time frame, the number of reference signalstransmitted by the base station may scale proportionally to the numberof UEs. The larger number of reference signals may be problematic forthe communications system (e.g., because of the large number ofresources required to transmit the reference signals as well as thepotential for collisions between reference signals intended fordifferent UEs). Additionally, such a large number of reference signalsmay place an unnecessary computational burden on the UEs, which mayattempt to decode and evaluate each received reference signal todetermine an optimal beam pair. Accordingly, considerations formanagement of beam refinement are discussed herein. Such considerationsinclude the use of scrambling sequences applied to the referencesignals. In some aspects, the scrambling sequences may be determinedbased on the set of resources over which a given UE sends its accessrequest. The correspondence between the resources and scramblingsequences may allow a receiver (e.g., the UE, base station, etc.) toidentify relevant reference signals to be considered in determininguplink and/or downlink beam pairs. Additionally, the scramblingsequences may effectively spread the reference signals in a code domain,such that multiple reference signals may be transmitted over the sameset of time-frequency resources and be separated via spatial and codedomain processing by a receiver.

Aspects of the disclosure are initially described in the context of awireless communications system. Aspects of the disclosure are thendescribed in terms of beam refinement illustrations, resource grids, andprocess flows. Aspects of the disclosure are further illustrated by anddescribed with reference to apparatus diagrams, system diagrams, andflowcharts that relate to scrambling sequences for reference signalsduring beam refinement.

FIG. 1 illustrates an example of a wireless communications system 100 inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes base stations 105, UEs 115, and acore network 130. In some examples, the wireless communications system100 may be a Long Term Evolution (LTE) network, LTE-Advanced (LTE-A)network, or a 5G new radio (NR) network. In some cases, wirelesscommunications system 100 may support enhanced broadband communications,ultra-reliable (i.e., mission critical) communications, low latencycommunications, and communications with low-cost and low-complexitydevices. Wireless communications system 100 may support scramblingsequences for reference signals during beam refinement.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Each base station 105 may providecommunication coverage for a respective geographic coverage area 110.Communication links 125 shown in wireless communications system 100 mayinclude uplink transmissions from a UE 115 to a base station 105, ordownlink transmissions, from a base station 105 to a UE 115. Controlinformation and data may be multiplexed on an uplink channel or downlinkchannel according to various techniques. Control information and datamay be multiplexed on a downlink channel, for example, using timedivision multiplexing (TDM) techniques, frequency division multiplexing(FDM) techniques, or hybrid TDM-FDM techniques. In some examples, thecontrol information transmitted during a transmission time interval(TTI) of a downlink channel may be distributed between different controlregions in a cascaded manner (e.g., between a common control region andone or more UE-specific control regions).

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile station, a subscriber station, a mobile unit, asubscriber unit, a wireless unit, a remote unit, a mobile device, awireless device, a wireless communications device, a remote device, amobile subscriber station, an access terminal, a mobile terminal, awireless terminal, a remote terminal, a handset, a user agent, a mobileclient, a client, or some other suitable terminology. A UE 115 may be acellular phone, a personal digital assistant (PDA), a wireless modem, awireless communication device, a handheld device, a tablet computer, alaptop computer, a cordless phone, a personal electronic device, ahandheld device, a personal computer, a wireless local loop (WLL)station, an Internet of things (IoT) device, an Internet of Everything(IoE) device, a machine type communication (MTC) device, an appliance,an automobile, or the like.

In some cases, a UE 115 may also be able to communicate directly withother UEs (e.g., using a peer-to-peer (P2P) or device-to-device (D2D)protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the coverage area 110 of a cell. Other UEs115 in such a group may be outside the coverage area 110 of a cell, orotherwise unable to receive transmissions from a base station 105. Insome cases, groups of UEs 115 communicating via D2D communications mayutilize a one-to-many (1:M) system in which each UE 115 transmits toevery other UE 115 in the group. In some cases, a base station 105facilitates the scheduling of resources for D2D communications. In othercases, D2D communications are carried out independently of a basestation 105.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines, i.e., Machine-to-Machine (M2M) communication. M2M or MTC mayrefer to data communication technologies that allow devices tocommunicate with one another or a base station without humanintervention. For example, M2M or MTC may refer to communications fromdevices that integrate sensors or meters to measure or captureinformation and relay that information to a central server orapplication program that can make use of the information or present theinformation to humans interacting with the program or application. SomeUEs 115 may be designed to collect information or enable automatedbehavior of machines. Examples of applications for MTC devices includesmart metering, inventory monitoring, water level monitoring, equipmentmonitoring, healthcare monitoring, wildlife monitoring, weather andgeological event monitoring, fleet management and tracking, remotesecurity sensing, physical access control, and transaction-basedbusiness charging.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., S1, etc.). Base stations105 may communicate with one another over backhaul links 134 (e.g., X2,etc.) either directly or indirectly (e.g., through core network 130).Base stations 105 may perform radio configuration and scheduling forcommunication with UEs 115, or may operate under the control of a basestation controller (not shown). In some examples, base stations 105 maybe macro cells, small cells, hot spots, or the like. Base stations 105may also be referred to as eNodeBs (eNBs) 105, next generation NodeBs(gNBs) 105, etc.

In some cases, wireless communications system 100 may be a packet-basednetwork that operates according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may insome cases perform packet segmentation and reassembly to communicateover logical channels. A Medium Access Control (MAC) layer may performpriority handling and multiplexing of logical channels into transportchannels. The MAC layer may also use Hybrid Automatic Repeat Request(HARD) to provide retransmission at the MAC layer to improve linkefficiency. In the control plane, the Radio Resource Control (RRC)protocol layer may provide establishment, configuration, and maintenanceof an RRC connection between a UE 115 and a base station 105, or corenetwork 130 supporting radio bearers for user plane data. At thephysical (PHY) layer, transport channels may be mapped to physicalchannels.

Wireless communications system 100 may support operation on multiplecells or carriers, a feature which may be referred to as carrieraggregation (CA) or multi-carrier operation. A carrier may also bereferred to as a component carrier (CC), a layer, a channel, etc. Theterms “carrier,” “component carrier,” and “channel” may be usedinterchangeably herein. A UE 115 may be configured with multipledownlink CCs and one or more uplink CCs for carrier aggregation. Carrieraggregation may be used with both frequency division duplex (FDD) andtime division duplex (TDD) component carriers.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider bandwidth, shorter symbol duration, shorterTTIs, and modified control channel configuration. In some cases, an eCCmay be associated with a carrier aggregation configuration or a dualconnectivity configuration (e.g., when multiple serving cells have asuboptimal or non-ideal backhaul link). An eCC may also be configuredfor use in unlicensed spectrum or shared spectrum (where more than oneoperator is allowed to use the spectrum). An eCC characterized by widebandwidth may include one or more segments that may be utilized by UEs115 that are not capable of monitoring the whole bandwidth or prefer touse a limited bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration may beassociated with increased subcarrier spacing. A TTI in an eCC mayconsist of one or multiple symbols. In some cases, the TTI duration(that is, the number of symbols in a TTI) may be variable. In somecases, an eCC may utilize a different symbol duration than other CCs,which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration isassociated with increased subcarrier spacing. A device, such as a UE 115or base station 105, utilizing eCCs may transmit wideband signals (e.g.,20, 40, 60, 80 MHz, etc.) at reduced symbol durations (e.g., 16.67microseconds). A TTI in an eCC may consist of one or multiple symbols.In some cases, the TTI duration (that is, the number of symbols in aTTI) may be variable.

A shared radio frequency spectrum band may be utilized in an NR sharedspectrum system. For example, an NR shared spectrum may utilize anycombination of licensed, shared, and unlicensed spectrums, among others.The flexibility of eCC symbol duration and subcarrier spacing may allowfor the use of eCC across multiple spectrums. In some examples, NRshared spectrum may increase spectrum utilization and spectralefficiency, specifically through dynamic vertical (e.g., acrossfrequency) and horizontal (e.g., across time) sharing of resources. Whenoperating in unlicensed radio frequency spectrum bands, wireless devicessuch as base stations 105 and UEs 115 may employ listen-before-talk(LBT) procedures to ensure the channel is clear before transmittingdata. In some cases, operations in unlicensed bands may be based on a CAconfiguration in conjunction with CCs operating in a licensed band.Operations in unlicensed spectrum may include downlink transmissions,uplink transmissions, or both. Duplexing in unlicensed spectrum may bebased on FDD, TDD, or a combination of both.

Wireless communications system 100 may operate in an ultra-highfrequency (UHF) region using frequency bands from 300 MHz to 3 GHz. Thisregion may also be known as the decimeter band, since the wavelengthsrange from approximately one decimeter to one meter in length. UHF wavesmay propagate mainly by line of sight, and may be blocked by buildingsand environmental features. However, the waves may penetrate wallssufficiently to provide service to UEs 115 located indoors. Transmissionof UHF waves is characterized by smaller antennas and shorter range(e.g., less than 100 km) compared to transmission using the smallerfrequencies (and longer waves) of the high frequency (HF) or very highfrequency (VHF) portion of the spectrum. Wireless communications system100 may also operate in a super high frequency (SHF) region usingfrequency bands from 3 GHz to 30 GHz, otherwise known as the centimeterband. In some cases, wireless communication system 100 may also utilizeextremely high frequency (EHF) portions of the spectrum (e.g., from 30GHz to 300 GHz), also known as the millimeter band. Systems that usethis region may be referred to as millimeter wave (mmW) systems. Thus,EHF antennas may be even smaller and more closely spaced than UHFantennas. In some cases, this may facilitate use of antenna arrayswithin a UE 115 (e.g., for directional beamforming). However, EHFtransmissions may be subject to even greater atmospheric attenuation andshorter range than UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions.

Wireless communications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105. Devices operatingin mmW, SHF, or EHF bands may have multiple antennas to allowbeamforming. Beamforming may also be employed outside of these frequencybands (e.g., in any scenario in which increased cellular coverage isdesired). That is, a base station 105 may use multiple antennas orantenna arrays to conduct beamforming operations for directionalcommunications with a UE 115. Beamforming (which may also be referred toas spatial filtering or directional transmission) is a signal processingtechnique that may be used at a transmitter (e.g., a base station 105)to shape and/or steer an overall antenna beam in the direction of atarget receiver (e.g., a UE 115). This may be achieved by combiningelements in an antenna array in such a way that transmitted signals atparticular angles experience constructive interference while othersexperience destructive interference. For example, base station 105 mayhave an antenna array with a number of rows and columns of antenna portsthat the base station 105 may use for beamforming in its communicationwith UE 115. Signals may be transmitted multiple times in differentdirections (e.g., each transmission may be beamformed differently). AmmW receiver (e.g., a UE 115) may try multiple beams (e.g., antennasubarrays) while receiving the signals. Each of these beams may bereferred to as a receive beam in aspects of the present disclosure.

Multiple-input multiple-output (MIMO) wireless systems use atransmission scheme between a transmitter (e.g., a base station 105) anda receiver (e.g., a UE 115), where both transmitter and receiver areequipped with multiple antennas. In some cases, the antennas of a basestation 105 or UE 115 may be located within one or more antenna arrays,which may support beamforming or MIMO operation. One or more basestation antennas or antenna arrays may be collocated at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may use multiple antennas orantenna arrays to conduct beamforming operations for directionalcommunications with a UE 115.

Synchronization (e.g., cell acquisition) may be performed usingsynchronization signals or channels transmitted by a network entity(e.g., a base station 105). A base station may transmit synchronizationsignal (SS) blocks containing discovery reference signals. SS blocks mayinclude a primary synchronization signal (PSS), a secondarysynchronization signal (SSS), or a physical broadcast channel (PBCH). AUE 115 attempting to access a wireless network (e.g., an initial access,beam recovery, handover) may perform a cell search by detecting a PSSfrom a base station 105. The PSS may enable synchronization of symboltiming and may indicate a physical layer identity value. The PSS may beutilized to acquire timing and frequency as well as a physical layeridentifier. The UE 115 may then receive an SSS. The SSS may enable radioframe synchronization, and may provide a cell group identity value. Thecell group identity value may be combined with the physical layeridentifier to form the physical cell identifier (PCID), which identifiesthe cell. The SSS may also enable detection of a duplexing mode and acyclic prefix (CP) length. An SSS may be used to acquire other systeminformation (e.g., subframe index). The PBCH may be used to acquireadditional system information needed for acquisition (e.g., bandwidth,frame index, etc.). For example, the PBCH may carry master informationblock (MIB) and one or more system information blocks (SIBs) for a givencell.

Because a base station 105 may not know the locations of devicesattempting to synchronize with a cell of the base station, SS blocks maybe successively transmitted in a beamswept manner (e.g., in multipledirections across multiple symbol periods). A UE 115 may receive one ormore of the SS blocks and determine a suitable downlink beam pair (e.g.,based on a signal quality of the SS block being greater than athreshold). However, the beams over which the SS blocks are transmittedmay be relatively coarse (e.g., broad) and may have low beamforminggains. Accordingly, communications between the UE 115 and base station105 may benefit from beam refinement, in which narrower uplink anddownlink receive and transmit beams of higher beamforming gains areselected. The width of a given beam (e.g., a narrow beam, a broad beam)may be modified by adjusting weighting of one or more of the elements ina transmitting or receiving antenna array. Such adjustments may beempirically determined by a receiving device (e.g., based onmeasurements of one or more reference signals). Each UE 115 attemptingto access a given cell may receive a set of downlink reference signalsand transmit a set of uplink reference signals to enable such beamrefinement. However, because of the potential for multiple UEs 115 toaccess a given cell within a certain time period, the number ofreference signals may be relatively large. Attempting to process all ofthese reference signals may unnecessarily burden the UE 115 (e.g.,increasing processing latency and/or power consumption).

In aspects of the present disclosure, uplink and downlink referencesignals associated with different beams may be scrambled using differentscrambling sequences. According to some aspects, the set of scramblingsequences available for a given reference signal may be determined basedon the resources (e.g., time-frequency resources, preamble identifier,etc.) over which the UE 115 transmits an access request. Such anassociation between scrambling sequences and access resources (e.g.,which may be referred to as physical random access channel (PRACH)resources) may provide for separability between reference signalsintended for UEs 115 that transmit access requests over separate PRACHresources. For example, a given set of PRACH resources (e.g.,time-frequency resources and preamble identifier) may be associated witha given set of scrambling sequences. Another set of PRACH resources(e.g., the same time-frequency resources but a different preambleidentifier, a different set of time-frequency resources) may beassociated with a second set of scrambling sequences.

Although described in the context of initial cell access, it is to beunderstood that the described techniques for beam refinement may applyin various circumstances. Considered scenarios in addition to an accessprocedure include handover, beam recovery (e.g., after a radio linkfailure), system access based on paging, etc. For example, beamrefinement may be performed during handover of a UE 115 to a neighboringcell. As with the initial access techniques described herein, beamrefinement for handover (e.g., as well as beam recovery or system accessbased on paging) may employ scrambling of reference signals. In somecases, the scrambling sequences for the reference signals may beimplicitly determined (e.g., based on a set of resources over which someprior transmission, such as a synchronization signal, was received) orthey may be explicitly indicated (e.g., based on an indicator includedin a previous transmission). For example, during a handover procedure, aUE 115 may receive a handover command which includes an indicator of aset of potential scrambling sequences which may be used for downlinkand/or uplink reference signals. Additionally or alternatively, a UE 115may receive a handover command that includes an indicator of a set ofcontention-free or limited contention access resources, which may thenbe used for determining a set of scrambling sequences for downlinkand/or uplink reference signals. Accordingly, though various signalsbelow are described in terms of the random access procedure (e.g.,access request, access response), it is to be understood that thedescribed concepts may be easily extended to other beam refinementprocedures.

FIG. 2 illustrates an example of a wireless communications system 200that supports scrambling sequences for reference signals during beamrefinement in accordance with various aspects of the present disclosure.Wireless communications system 200 includes a base station 105-a and UEs115-a and 115-b, each of which may be an example of the correspondingdevice described with reference to FIG. 1.

Wireless communications system 200 may operate in frequency ranges thatare associated with beamformed transmissions between base station 105-aand UEs 115-a and 115-b. For example, wireless communications system 200may operate using mmW frequency ranges. As a result, signal processingtechniques such as beamforming may be used to improve communicationquality.

By way of example, base station 105-a may contain multiple antennas. Insome cases, each antenna may transmit a phase-shifted version of asignal such that the phase-shifted versions constructively interfere incertain regions and destructively interfere in others (e.g., in order tosteer the beams in a desired direction and/or to control the width ofthe beam). The region in which strong constructive interference occursmay in some cases be referred to as a beam. Weights may be applied tothe various phase-shifted versions. Such techniques (or similartechniques) may serve to increase the coverage area 110-a of the basestation 105-a or otherwise benefit the wireless communications system200.

Transmit beams 205 represent examples of beams over which informationmay be transmitted. Accordingly, each transmit beam 205 may be directedfrom base station 105-a toward a different region of the coverage area110-a, and, in some cases, two or more beams may overlap. Multipletransmit beams 205 may be transmitted simultaneously or sequentially. Ineither case, UE 115-a and/or 115-b may be capable of receiving one ormore transmit beams 205 via a receive beam 210.

In one example, UE 115-a may form receive beams 210-a and 210-b. Similarto base station 105-a, UE 115-a may contain multiple antennas. In somecases, receive beams 210-a and 210-b may each receive signals sent overtransmit beam 205-a and transmit beam 205-b. Because the signaltransmitted over transmit beam 205-a experiences different path lossesand phase shifts on its way to the respective antennas of UE 115-a andbecause each receive beam 210-a and 210-b weights antennas of UE 115-adifferently, the signal received over receive beam 210-a may havedifferent signal properties from the signal received over receive beam210-b. Similar differences in signal quality may be observed for thesignal transmitted over transmit beam 205-b. UE 115-a may select atransmit beam 205 and a receive beam 210 based on the received signalquality. The transmit beam 205 and corresponding receive beam 210 may bereferred to as a beam pair. Various methods for identifying a desiredbeam pair are considered within the scope of the present disclosure. Forexample, in some cases, base station 105-a may repeat transmissions overmultiple transmit beams 205 (e.g., in every direction), and UE 115-a mayreport a beam for receiving downlink transmissions (e.g., transmit beam205-a, 205-b, 205-c, or 205-d) with a signal quality above a thresholdor may report the strongest received beam. These transmit beams 205 maybe broadcast beams directed to multiple UEs 115 and may each beassociated with an SS block. Additionally or alternatively, base station105-a may transmit multiple UE-specific transmit beams 205 over a smallangular region (e.g., to assist UE 115-a in fine-tuning the selectedtransmit beam 205). Further, in some cases, base station 105-a mayrepeat transmission of a single transmit beam (e.g., transmit beam205-a) multiple times (e.g., to allow UE 115-a to compare multiplereceive beams 210-a and 210-b).

Analogous beam pair determinations may be performed at UE 115-b. Thatis, UE 115-b may form one or more receive beams 210-c and/or 210-d. Thereceive beams 210-c and 210-d may each receive signals transmitted overone or more transmit beams 205 (e.g., transmit beams 205-a, 205-b,205-c, or 205-d). In aspects of the present disclosure, each transmitbeam 205 may carry a respective reference signal. Similarly, eachreceive beam 210 may be employed to receive one or more referencesignals. UEs 115-a and 115-b may measure reference signals of thevarious transmit beams 205 received over the various receive beams 210and determine a beam pair. For example, the beam pair for UE 115-a mayinclude transmit beam 205-b and receive beam 210-a, while the beam pairfor UE 115-b may include transmit beam 205-d and receive beam 210-d.

It is to be understood, that while the examples above are described interms of downlink transmissions (i.e., such that the transmit beams 205originate at the base station 105-a), analogous considerations foruplink transmissions are included in the scope of the presentdisclosure. For example, UEs 115-a and 115-b may transmit referencesignals over multiple transmit beams 210, which are received at basestation 105-a over one or more receive beams 205.

FIG. 3A illustrates an example of a synchronization transmission 300-ain accordance with various aspects of the present disclosure.Synchronization transmission 300-a may represent aspects of techniquesperformed within wireless communications systems 100 or 200 as describedabove. As illustrated, synchronization transmission 300-a may originateat base station 105-b, which may be an example of the correspondingdevice described with reference to FIGS. 1 and 2.

Synchronization transmission 300-a may include SS blocks transmittedover transmit beams 305-a and 305-b in a beamswept fashion over asynchronization period 310. For example, synchronization period 310 mayinclude multiple time intervals 315 (e.g., which may be symbol periods,fractions thereof, subframes, or any other suitable time interval). TheSS block of transmit beam 305-a may be transmitted in time interval315-a, and the SS block of transmit beam 305-b may be transmitted intime interval 315-b. Alternatively, the SS blocks may be transmittedover the respective transmit beams 305 in the same time interval 315-b.

FIG. 3B illustrates an example of a PRACH configuration 300-b. PRACHconfiguration 300-b includes UEs 115-c and 115-d, each of which may bean example of the corresponding devices described above with referenceto FIGS. 1, 2, and 3A. For example, UEs 115-c and 115-d may be locatedin different regions of a coverage area of base station 105-b asdescribed with reference to FIG. 3A. Accordingly, UE 115-c may receivethe SS block transmitted in time-interval 315-a with a signal qualityexceeding a threshold while UE 115-d may receive the SS blocktransmitted in time interval 315-b with a signal quality exceeding thethreshold. UEs 115-c and 115-d may then transmit respective accessrequests over respective uplink transmit beams 340-a and 340-b (e.g.,which may be derived from receive beams used for receiving therespective downlink transmit beams 305 in FIG. 3A).

For example, UEs 115-c and 115-d may use resources 350 within an accessrequest period 345 to transmit the access requests. As illustrated, UEs115-c and 115-d use respective PRACH resources 350 of access requestperiod 345 to transmit the access requests. For example, access requestperiod 345 may be divided into access request interval 325-a, accessrequest interval 325-b, and frequency regions 330 for the sake ofexplanation. In some examples, access request intervals 325 may be asame interval as time intervals 315 of FIG. 3A. In other examples,access request intervals 325 may be longer or shorter than timeintervals 315 (e.g., access request intervals 325 may span multiple timeintervals 315). Each time interval 315 of FIG. 3A may be mapped torespective PRACH resources 350 (e.g., based on system information orpreconfigured parameters). Accordingly, UE 115-c may, upon selecting adownlink transmit beam transmitted in an SS block in time period 315-a,identify PRACH resources 350-a on which to transmit the access requestover transmit beam 340-a. Similarly, UE 115-d may, upon selecting adownlink transmit beam transmitted in the SS block in time period 315-b,identify PRACH resources 350-b on which to transmit the access requestover transmit beam 340-b. In some aspects, the PRACH resources 350 mayinclude a preamble identifier of a set of preamble identifiers (e.g.,multiple PRACH resources 350 may share the same time-frequency resourcesbut be associated with different preamble identifiers). Base station105-b may expect access requests within access request period 345 andmay accordingly perform beam sweeping of receive beams corresponding tothe beam sweeping used for transmission of the SS blocks (e.g., suchthat base station 105-b receives access requests from a given segment ofthe coverage area using respective receive beams).

FIG. 4 illustrates an example of a random access response configuration400 that supports scrambling sequences for reference signals during beamrefinement in accordance with various aspects of the present disclosure.In some examples, random access response configuration 400 may representaspects of wireless communications system 100. Random access responseconfiguration 400 includes base station 105-c and UEs 115-e and 115-f,each of which may be an example of the corresponding device describedabove with reference to FIGS. 1-3B.

As illustrated, base station 105-c may transmit a random access responseand associated control information over a relatively broad downlinktransmit beam 415 (e.g., which may be the same transmit beam over whichthe SS block was transmitted in the synchronization period 310 of FIG.3A). Similarly, UEs 115-e and 115-g may receive the random accessresponse over relatively broad downlink receive beams 420-a and 420-b(e.g., which may be the same receive beams over which the SS blocks werereceived in the synchronization period 310 of FIG. 3A). Additionally oralternatively, base station 105-c may transmit a contention resolutionmessage with the random access response over transmit beam 415.

In addition to the random access response transmission and response, thebase station 105-c and UEs 115-e and 115-f may perform beam refinementin order to identify an optimized beam pair for future communications.In order to support the beam refinement, base station 105-c may transmitreference signals over respective candidate downlink transmit beams 405.Similarly, the UEs 115-e and 115-f may attempt to receive the referencesignals over multiple candidate downlink receive beams 410. For example,UE 115-e may perform a sweep over downlink receive beams 410-a and 410-bto receive the reference signal transmitted over downlink transmit beam405-a. Additionally, UE 115-e may perform a sweep over downlink receivebeams 410-c and 410-d to receive the reference signal transmitted overdownlink transmit beam 405-b. Similarly, UE 115-f may perform a sweepover downlink receive beams 410-e and 410-f to receive the referencesignal transmitted over downlink transmit beam 405-c. Additionally, UE115-f may perform a sweep over downlink receive beams 410-g and 410-h toreceive the reference signal transmitted over downlink transmit beam405-d. Each UE 115 may identify an optimal downlink transmit beam 405and downlink receive beam 410. The various candidate downlink transmitbeams may be selected by the base station 105-c for beam refinement toestablish optimized downlink transmit and receive beam pairs for each UE115. The candidate beams may be the same width as the beams used for SSblocks. Alternatively, the candidate beams may be narrower or wider.

Each UE 115 may search for the random access response and referencesignals over a given search window 425 after the transmission of itsaccess request. For example, UE 115-e may search over search window425-a, and UE 115-f may search over search window 425-b (e.g., UE 115-emay have transmitted its access request before UE 115-f). Althoughillustrated as different windows of time, search windows 425 formultiple UEs 115 may be the same (e.g., when access requests aretransmitted in a same time period using different frequency resources orpreamble identifiers). As illustrated, the search windows 425 may besegmented into time intervals 430 (e.g., which may be subframes inaspects of the present example, although other time divisions are alsoconsidered such as symbols, slots, mini-slots, and fractions thereof).For example, shorter search windows 425 may be employed for devices withpower constraints.

Each time interval 430 may be segmented into a control region 465 and adata region 460. As an example, each control region 465 may contain acommon search space 435 (e.g., which may be transmitted over broaddownlink transmit beam 415 and received over a broad downlink receivebeam 420). Downlink control information (DCI) in the common search space435 may indicate the presence of reference signals and/or a randomaccess response in the data region 460 of the corresponding timeinterval 430.

For example, time interval 430-a may contain common search space 435-a,which may include a DCI transmission indicating the presence ofreference signals. In some examples, the DCI may be scrambled with anidentifier associated with a random access response (e.g., random accessradio network temporary identifier (RA-RNTI)). UE 115-e and UE 115-f mayreceive the control information (e.g., by detecting DCI scrambled withRA-RNTI) and identify reference signal resources 440-a within the dataregion 460 of time interval 430-a. As illustrated, reference signalresources 440-a may contain reference signals transmitted overrespective candidate downlink transmit beams 405. As illustrated in FIG.4, the reference signal resources 440-a may be shared by referencesignals intended for multiple UEs 115. In some examples, the referencesignal resources 440-a may be divided into different sets of referencesignal resources, each associated with different sets of referencesignals. For example, there may be N scrambling sequences, which aredivided into M sets of N/M scrambling sequences, where each UE 115 maybe assigned one of the M sets based on the set of resources used for theaccess request message. Additionally, there may be K reference signalresource locations (e.g., each associated with every Kth subcarrier),where K may be the same or different than M, in reference signalresources 440-a, such that each reference signal resource location maycarry up to N/K reference signals transmitted concurrently. In oneexample, a single combined scrambling sequence may be defined, whereeach of the N scrambling sequences are indexed portions of the combinedscrambling sequence.

DCI in common search space 435-b of time interval 430-b may indicate thepresence of a random access response message 450 in time interval 430-b.Based on decoding the control information (e.g., which may also bescrambled with RA-RNTI), UEs 115-e and 115-f may process random accessresponse 450. Like the control information, random access responsemessage 450 may be transmitted over broad downlink transmit beam 415 andreceived over broad downlink receive beams 420. In some examples, thetime interval 430-b may, instead of or in addition to time interval430-a, include reference signal resources 440-b, which may be within aregion of random access response 450, or in different time-frequencyresources of time interval 430-b. As illustrated, reference signalresources 440-b may contain reference signals transmitted overrespective candidate downlink transmit beams 405. In some cases, thepresence of reference signal resources 440-b may be indicated by thesame DCI in common search space 435-b that indicates the presence of therandom access response message 450 or may be indicated by a separate DCIin the same or a former time interval within the search windows 425.

The reference signals transmitted over reference signal resources 440-aor 440-b may be scrambled (e.g., such that multiple reference signalsmay be transmitted over the same set of time-frequency resources). Thescrambling sequences for each reference signal may be based on the PRACHresources with which the access request was transmitted. For example,each set of time-frequency resources and preamble identifier for anaccess request transmission may have an associated set of scramblingsequences (e.g., which may be known a priori to the UE 115, may beconveyed in a system information transmission, or may be configured forthe UE 115 using dedicated signaling). Because each UE 115 knows thePRACH resources it used to transmit the access request, it may identifyone or more potential scrambling sequences of the set with whichreference signals intended for it are scrambled. Accordingly, uponidentifying that a given time interval 430 contains reference signalresources 440, the UE 115 may attempt to descramble the referencesignals based on the potential scrambling sequences. Upon successfullydetecting a reference signal (e.g., based on a correlation with theexpected sequence), the UE 115 may determine that the reference signalwas intended for it and perform signal measurements accordingly. In thecase that one or more reference signals are received over multiplecandidate downlink receive beams 410, the signal quality of thereference signals received over downlink receive beams 410 may beevaluated.

The reference signals may be transmitted within the same time as therandom access response as shown in time interval 430-b, before therandom access response as shown in time interval 430-a, or in a timeinterval of the search window 425 after the random access response (notshown). Such flexibility may improve resource efficiency for thewireless communications system.

FIG. 5 illustrates an example of an access report configuration 500 thatsupports scrambling sequences for reference signals during beamrefinement in accordance with various aspects of the present disclosure.In some examples, access report configuration 500 may implement aspectsof wireless communications system 100. Access report configuration 500includes base station 105-d and UE 115-g, each of which may be anexample of the corresponding devices described above with reference toFIGS. 1-4.

After receiving the random access response and any associated referencesignals, a UE 115 (e.g., UE 115-g) may transmit a report to base station105-d. In some cases, a grant for the report may be contained within therandom access response. The report may include information regarding aselected downlink candidate transmit beam 405, as described above withreference to FIG. 4, as well as any other relevant access information(e.g., a temporary identifier for the UE 115-g, etc.). As illustrated,the report may be transmitted from UE 115-g over broad uplink beam 515and received by base station 105-d over broad uplink receive beam 510.In some cases, broad uplink receive beam 510 and broad uplink transmitbeam 515 may be the same as or based on broad downlink transmit beam 410and broad downlink receive beam 415, respectively, as described abovewith reference to FIG. 4.

Along with the access report, UE 115-g may transmit reference signalsover respective uplink transmit beams 520-a and 520-b. Similarly, basestation 105-d may receive reference signals over uplink receive beams505. For example, base station 105-d may sweep over uplink receive beams505-a and 505-b to receive a reference signal transmitted over uplinktransmit beam 520-a. Additionally, base station 105-d may sweep overuplink receive beams 505-c and 505-d to receive a reference signaltransmitted over uplink transmit beam 520-b. Accordingly, UE 115-g andbase station 105-d may determine an optimal beam pair for uplinkcommunications, which may or may not be the same as the optimal beampair for downlink communications.

As mentioned above, the grant for the report may be included in therandom access response. Accordingly, UE 115-g may determine, based onthe random access response, a time interval 535 in which to transmit thereport. UE 115-g may transmit the report over report resources 545 of adata region 560 of time interval 535. The uplink reference signals foruplink transmit beams 520-a and 520-b may be transmitted in a same timeinterval 535 as the report (e.g., as illustrated in FIG. 5) or before orafter transmitting the report. For example, the random access responsemay provide an offset for the reference signals from the report.Additionally or alternatively, UE 115-g may be configured with a searchwindow 530 in which to search for a grant for transmitting the referencesignals.

UE 115-g may transmit uplink reference signals over reference signalresources 550. As illustrated, reference signal resources 550 may bedivided in time and/or frequency. Multiple reference signals may bemultiplexed over a given set of resources (e.g., using scramblingsequences). For example, scrambling sequences for the reference signalsmay be selected from a set of potential scrambling sequences, which mayin turn be based on the PRACH resources over which the initial accessrequest was transmitted. As an example, the set of potential scramblingsequences may be the same as the set of potential scrambling sequencesfor the downlink reference signals. Alternatively, the scramblingsequences for the uplink reference signals may be determined based on anidentifier received from base station 105-d. For initial access, theidentifier may be received in the random access response. For otheraccess procedures (e.g., handover, beam recovery, access based onpaging), the identifier may be received in other communications such asa handover command. For example, there may be N scrambling sequences forthe uplink reference signals, which are divided into M sets of N/Mscrambling sequences, where each UE 115 may be assigned one of the Msets based on an identifier received in the random access response orthe set of resources used for the access request message. There may be Kreference signal resource locations (e.g., each associated with everyKth subcarrier), where K may be the same or different than M, inreference signal resources 550, such that each reference signal resourcelocation may carry up to N/K reference signals transmitted concurrently.In one example, a single combined scrambling sequence may be defined,where each of the N scrambling sequences are indexed portions of thecombined scrambling sequence.

FIG. 6 illustrates an example of a process flow 600 that supportsscrambling sequences for reference signals during beam refinement inaccordance with various aspects of the present disclosure. Process flow600 includes base station 105-e and UEs 115-h and 115-i, each of whichmay be an example of the corresponding devices described above withreference to FIGS. 1-5.

At 605, base station 105-e may transmit (e.g., and UE 115-h may receive)an SS block over a relatively coarse beam. Additionally, at 610, basestation 105-e may transmit (e.g., and UE 115-i may receive) an SS blockover another coarse beam. Base station 105-e may transmit the SS blocksat 605 and 610 within a synchronization period, as described above withreference to FIG. 3. For example, base station 105-e may transmit the SSblocks at 605 and 610 sequentially (e.g., in a beamswept fashion, asillustrated) or simultaneously. Thus, the respective SS blocks may beassociated with different sets of time-frequency resources.

At 615, UE 115-h may transmit (e.g., and base station 105-e may receive)an access request. Similarly, at 620, UE 115-i may transmit (e.g., andbase station 105-e may receive) an access request. As with the SSblocks, the access requests may be transmitted and received overrelatively broad beams. In some aspects, each access request may betransmitted over a respective set of PRACH resources includingtime-frequency resources and a preamble identifier. The PRACH resourcesmay be based on the resources over which the respective SS blocks werereceived. For example, a given SS block may have a designated set oftime-frequency resources and set of preamble identifiers over which anydevices selecting the beam associated with the SS block may transmit anaccess request. The access requests may be transmitted at the same timeor at different times (e.g., as illustrated). In some cases, UE 115-h orUE 115-i may transmit a second message accompanying the access request.For example, UE 115-h or UE 115-i may transmit the second message in aset of resources that overlap or are distinct from the set of PRACHresources. The second message may, for example, convey information suchas the UE ID, and may be used in contention resolution. In someexamples, the resources or scrambling for the second message may bebased on the set of PRACH resources. For example, the second message maybe scrambled based on the preamble identifier (e.g., using a scramblingcode that is selected based on the preamble identifier). As anotherexample, the time-frequency resources for the second message may bebased on the time-frequency resources used for the access request, ormay be based on the preamble identifier.

At 625, base station 105-e (e.g., and UEs 115-h and 115-i) may identifyone or more sets of scrambling sequences based on the PRACH resourcesover which the respective access requests were transmitted. For example,the PRACH resources of the access request received at 615 may beassociated with a first set of scrambling sequences, while the PRACHresources of the access request received at 620 may be associated with asecond set of scrambling sequences. In some cases, base station 105-eand UEs 115-h and 115-i may identify sets of downlink scramblingsequences and uplink scrambling sequences at 625. In some cases, thesets of downlink and uplink scrambling sequences may be the same. Wherethe UE 115-h or UE 115-i transmits a second message with the accessrequest, the set of scrambling sequences identified by the UE 115-h orUE 115-i may be further based on information conveyed by the secondmessage (e.g., UE ID).

At 635, base station 105-e may transmit (e.g., and UEs 115-h and 115-imay receive) a random access response. The random access response may betransmitted and received over a broad beam (e.g., which may be the sameas the beams over which the SS block was transmitted and received,respectively). The random access response may include respective grantsof uplink resources over which UEs 115-h and 115-i may transmit feedbackreports (e.g., at 655 and 660, as described below). In some cases, therandom access response is transmitted within a response window after thereception of the first access request (e.g., which may alternatively bereferred to as a random access message) at 615 and within a secondresponse window after the reception of the second access request at 620.

Along with the random access response, base station 105-e may transmit areference signal scrambled with one of the downlink scrambling sequencesof the first set of scrambling sequences to UE 115-h at 630. Althoughillustrated as occurring before the random access response, it is to beunderstood that the reference signal may be transmitted before, during,or after the random access response. In some cases, a TTI fortransmitting the reference signal may be indicated in a DCItransmission. Additionally, though only one reference signal is shown,multiple reference signals may be transmitted. Each reference signal maybe associated with a relatively narrow transmit beam and received overone or more relatively narrow receive beams of UE 115-h (e.g., UE 115-hmay sweep receive beams to detect the reference signals).

Similarly, base station 105-e may transmit a reference signal scrambledwith one of the downlink scrambling sequences of the second set ofscrambling sequences to UE 115-i at 640. Although illustrated asoccurring after the random access response, it is to be understood thatthe reference signal may be transmitted before, during, or after therandom access response. In some cases, a TTI for transmitting thereference signal may be indicated in a DCI transmission that is separatefrom the DCI associated with the random access response (e.g., alsoscrambled with RA-RNTI). Additionally, though only one reference signalis shown, multiple reference signals may be transmitted. Each referencesignal may be associated with a relatively narrow transmit beam andreceived over one or more relatively narrow receive beams of UE 115-i(e.g., UE 115-i may sweep receive beams to detect the referencesignals).

At 645, UEs 115-h and 115-i may identify respective downlink beam pairsbased on the reference signals. For example, UE 115-h may identify anoptimized downlink transmit beam and downlink receive beam (e.g.,downlink beam pair). Similar identification may be performed at UE115-i. The identifications may be based on measurements (e.g., referencesignal received power (RSRP), signal-to-noise ratio (SNR), etc.) of thevarious reference signals performed at the respective UEs 115.

At 650, UE 115-h may transmit an uplink reference signal and at 655 mayalso transmit a report. In some cases, the report transmitted at 655 maybe transmitted over a relatively broad beam (e.g., the same beam used totransmit the access request at 615). The report may include anindication of the identified downlink beam pair. In some cases, thereport may be transmitted with an initial layer-3 message. The initiallayer-3 message may convey, for example, the UE ID, and may be used forcontention resolution. As with the downlink reference signals, one ormore uplink reference signals may be transmitted at 650, and the uplinkreference signals may occur before, during, and/or after the report at655. The uplink reference signals may be scrambled with a scramblingsequence from the first set of scrambling sequences identified at 625.Additionally or alternatively, the scrambling sequences for the uplinkreference signals may be indicated by an indicator in the random accessresponse received at 635. In some cases, a TTI for transmission of theuplink reference signals may be indicated in the random access responsereceived at 635.

Similarly, at 660, UE 115-i may transmit an uplink reference signal andat 665 may transmit a report. In some cases, the report transmitted at665 may be transmitted over a relatively broad beam (e.g., the same beamused to transmit the access request at 620). The report may include anindication of the identified downlink beam pair. As with the downlinkreference signals, one or more uplink reference signals may betransmitted at 665, and the uplink reference signals may occur before,during, and/or after the report at 660. The uplink reference signals maybe scrambled with a scrambling sequence from the second set ofscrambling sequences identified at 625. Additionally or alternatively,the scrambling sequences for the uplink reference signals may beindicated by an indicator in the random access response received at 635.In some cases, a TTI for transmission of the uplink reference signalsmay be indicated in the random access response received at 635.

At 670, base station 105-e may identify an uplink beam pair forcommunication with each UE 115 based on the uplink reference signals.For example, base station 105-e may identify an optimized uplinktransmit beam and uplink receive beam from the reference signals from UE115-h. Similar identification may be performed for UE 115-i.

At 675, base station 105-e may independently establish communicationlinks with UE 115-h and UE 115-i. The respective communication links mayuse the downlink beam pairs identified at 645 and the uplink beam pairsidentified at 670.

FIG. 7 shows a block diagram 700 of a wireless device 705 that supportsscrambling sequences for reference signals during beam refinement inaccordance with aspects of the present disclosure. Wireless device 705may be an example of aspects of a base station 105 as described herein.Wireless device 705 may include receiver 710, base stationcommunications manager 715, and transmitter 720. Wireless device 705 mayalso include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 710 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to scramblingsequences for reference signals during beam refinement). Information maybe passed on to other components of the device. The receiver 710 may bean example of aspects of the transceiver 1035 described with referenceto FIG. 10. The receiver 710 may utilize a single antenna or a set ofantennas.

Base station communications manager 715 may be an example of aspects ofthe base station communications manager 1015 described with reference toFIG. 10. Base station communications manager 715 and/or at least some ofits various sub-components may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions of thebase station communications manager 715 and/or at least some of itsvarious sub-components may be executed by a general-purpose processor, adigital signal processor (DSP), an application-specific integratedcircuit (ASIC), an field-programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The base station communications manager 715 and/or at least some of itsvarious sub-components may be physically located at various positions,including being distributed such that portions of functions areimplemented at different physical locations by one or more physicaldevices. In some examples, base station communications manager 715and/or at least some of its various sub-components may be a separate anddistinct component in accordance with various aspects of the presentdisclosure. In other examples, base station communications manager 715and/or at least some of its various sub-components may be combined withone or more other hardware components, including but not limited to anI/O component, a transceiver, a network server, another computingdevice, one or more other components described in the presentdisclosure, or a combination thereof in accordance with various aspectsof the present disclosure.

Base station communications manager 715 may receive a first randomaccess message from a first UE over a first set of resources; transmit,in a first transmission time interval in response to the first randomaccess message, one or more downlink beam reference signals scrambledwith respective downlink scrambling sequences of a set of downlinkscrambling sequences; and receive first channel feedback informationfrom the first UE. In some cases, the set of downlink scramblingsequences selected from a set of sets of downlink scrambling sequencesis based on the first set of resources. Additionally, in some aspects,the first channel feedback information is based on measurements of thedownlink beam reference signals.

Transmitter 720 may transmit signals generated by other components ofthe device. In some examples, the transmitter 720 may be collocated witha receiver 710 in a transceiver module. For example, the transmitter 720may be an example of aspects of the transceiver 1035 described withreference to FIG. 10. The transmitter 720 may utilize a single antennaor a set of antennas.

FIG. 8 shows a block diagram 800 of a wireless device 805 that supportsscrambling sequences for reference signals during beam refinement inaccordance with aspects of the present disclosure. Wireless device 805may be an example of aspects of a wireless device 705 or a base station105 as described with reference to FIG. 7. Wireless device 805 mayinclude receiver 810, base station communications manager 815, andtransmitter 820. Wireless device 805 may also include a processor. Eachof these components may be in communication with one another (e.g., viaone or more buses).

Receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to scramblingsequences for reference signals during beam refinement, etc.).Information may be passed on to other components of the device. Thereceiver 810 may be an example of aspects of the transceiver 1035described with reference to FIG. 10. The receiver 810 may utilize asingle antenna or a set of antennas.

Base station communications manager 815 may be an example of aspects ofthe base station communications manager 1015 described with reference toFIG. 10. Base station communications manager 815 may also include PRACHcomponent 825, reference signal manager 830, and beam manager 835.

PRACH component 825 may receive a first random access message from afirst UE over a first set of resources. Additionally, PRACH component825 may receive a second random access message from a second UE over thefirst set of resources or a second set of resources. In some cases, thefirst and second sets of resources include time resources, frequencyresources, preamble resources, or a combination thereof.

Reference signal manager 830 may transmit, in a first TTI in response tothe first random access message, one or more downlink beam referencesignals scrambled with respective downlink scrambling sequences of a setof downlink scrambling sequences. Reference signal manager 830 mayselect the set of downlink scrambling sequences from a set of sets ofdownlink scrambling sequences based on the first set of resources. Insome cases, reference signal manager 830 may identify a set of uplinkscrambling sequences for one or more candidate uplink beam referencesignals and receive the one or more candidate uplink beam referencesignals scrambled with respective ones of the set of uplink scramblingsequences. Reference signal manager 830 may transmit, in the first TTIin response to the second random access message, one or more seconddownlink beam reference signals scrambled with respective downlinkscrambling sequences of a second set of downlink scrambling sequences.The second set of downlink scrambling sequences may be selected from theplurality of sets of downlink scrambling sequences based on the secondset of resources. Reference signal manager 830 may identify time andfrequency resources for the one or more downlink beam reference signalsbased on the first set of resources. In some cases, the set of uplinkscrambling sequences is identified based on the first set of resources,an indicator transmitted in a random access response to the first randomaccess message, a second indicator transmitted in a handover command, orsome combination thereof. In some cases, the random access responseincludes an indicator of a third TTI for transmission of candidateuplink beam reference signals from the first UE. In some cases, therandom access response includes a second indicator of a fourth TTI fortransmission of second uplink beam reference signals from the second UE.Additionally or alternatively, reference signal manager 830 may receivea data message from the first UE based on the first random accessmessage, where the set of downlink scrambling sequences are determinedbased on information within the data message.

Beam manager 835 may receive first channel feedback information from thefirst UE, where the first channel feedback information is based onmeasurements of the downlink beam reference signals. Beam manager 835may send one or more transmissions to the first UE via a candidatedownlink transmit beam selected based on the first channel feedbackinformation. Beam manager 835 may receive second channel feedbackinformation from the second UE, where the second channel feedbackinformation is based on measurements of the second downlink beamreference signals. In some cases, beam manager 835 may receive secondchannel feedback information from the second UE, where the secondchannel feedback information is based on measurements of the downlinkbeam reference signals.

Transmitter 820 may transmit signals generated by other components ofthe device. In some examples, the transmitter 820 may be collocated witha receiver 810 in a transceiver module. For example, the transmitter 820may be an example of aspects of the transceiver 1035 described withreference to FIG. 10. The transmitter 820 may utilize a single antennaor a set of antennas.

FIG. 9 shows a block diagram 900 of a base station communicationsmanager 915 that supports scrambling sequences for reference signalsduring beam refinement in accordance with aspects of the presentdisclosure. The base station communications manager 915 may be anexample of aspects of a base station communications manager 715, a basestation communications manager 815, or a base station communicationsmanager 1015 described with reference to FIGS. 7, 8, and 10. The basestation communications manager 915 may include PRACH component 920,reference signal manager 925, access manager 930, and beam manager 935.Each of these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

PRACH component 920 may receive signal 940 (e.g., via a receiver 710 or810), and may identify random access messages within a portion (e.g., arandom access channel) of the signal 940 (e.g., by correlating forrandom access sequences, or demodulation and decoding of the signal940). In some cases, PRACH component 920 may receive a first randomaccess message from a first UE over a first set of resources.Additionally, PRACH component 920 may receive a second random accessmessage from a second UE over the first set of resources or a second setof resources. In some cases, the first and second sets of resourcesinclude time resources, frequency resources, preamble resources, or acombination thereof. PRACH component 920 may pass information 945indicating the first and/or second sets of resources that the randomaccess messages are received over to reference signal manager 925.

Reference signal manager 925 may transmit, in a first TTI in response tothe first random access message, one or more downlink beam referencesignals scrambled with respective downlink scrambling sequences of a setof downlink scrambling sequences. For example, reference signal manager925 may pass signal 950 to a transmitter 720 or 820 including the one ormore scrambled downlink beam reference signals for transmission intime-frequency resources over which the scrambled downlink referencesignals are to be transmitted. Reference signal manager 925 may selectthe set of downlink scrambling sequences from a set of sets of downlinkscrambling sequences based on the first set of resources. In some cases,reference signal manager 925 may identify a set of uplink scramblingsequences for one or more candidate uplink beam reference signals andreceive the one or more candidate uplink beam reference signalsscrambled with respective ones of the set of uplink scramblingsequences.

Additionally, reference signal manager 925 may transmit, in the firstTTI in response to the second random access message, one or more seconddownlink beam reference signals scrambled with respective downlinkscrambling sequences of a second set of downlink scrambling sequences.The second set of downlink scrambling sequences may be selected from theplurality of sets of downlink scrambling sequences based on the secondset of resources. Reference signal manager 925 may identify time andfrequency resources for the one or more downlink beam reference signalsbased on the first set of resources from information 945. In some cases,the set of uplink scrambling sequences is identified based on the firstset of resources, an indicator transmitted in a random access responseto the first random access message, a second indicator transmitted in ahandover command, or some combination thereof. In some cases, the randomaccess response includes an indicator of a third TTI for transmission ofuplink candidate beam reference signals from the first UE. In somecases, the random access response includes a second indicator of afourth TTI for transmission of second uplink beam reference signals fromthe second UE. Additionally or alternatively, reference signal manager925 may receive a data message from the first UE (e.g., via a receiver710 or 810) based on the first random access message, where the set ofdownlink scrambling sequences are determined based on information withinthe data message. Reference signal manager 925 may downlink beamreference signal information 955 indicating the downlink beam referencesignals that the UE may measure and, accordingly, report on.

Access manager 930 may transmit (e.g., via a transmitter 720 or 820), ina second TTI, a random access response to the first and second UEs, therandom access response including respective grants of uplink resourcesfor first and second channel feedback information. Access manager 930may indicate, in a downlink control information transmission, a firstTTI for the transmitting of the one or more downlink beam referencesignals and the one or more second downlink beam reference signals basedon downlink beam reference signal information 955. In some cases, therandom access response is transmitted within a first response windowafter the reception of the first random access message and within asecond response window after the reception of the second random accessmessage, where the random access message are received via signal 940. Insome cases, the first TTI is prior to the second TTI or subsequent tothe second TTI. In some cases, the first TTI and the second TTI are asame TTI. Access manager may send uplink resource information 960indicating the uplink resources included in the grants for the first andsecond channel feedback information.

Beam manager 935 may receive the first channel feedback information fromthe first UE, where the first channel feedback information is based onmeasurements of the downlink beam reference signals. For example, beammanager 935 may receive a signal 965 and may demodulate and decode thesignal to determine the first channel feedback information. Beam manager935 may configure transmissions to be sent to the first UE via acandidate downlink transmit beam selected based on the first channelfeedback information. For example, beam manager 935 may pass beaminformation 970 to a transmitter 720 or 820 indicating one or moredownlink transmit beams. Beam manager 935 may receive the second channelfeedback information from the second UE, where the second channelfeedback information is based on measurements of the second downlinkbeam reference signals. Additionally or alternatively, the secondchannel feedback information may be based on measurements of the firstand second downlink beam reference signals. For example, similar to theprocess described above, beam manager 935 may receive a signal 965 andmay demodulate and decode the signal to determine the second channelfeedback information.

FIG. 10 shows a diagram of a system 1000 including a device 1005 thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure. Device1005 may be an example of or include the components of wireless device705, wireless device 805, or a base station 105 as described above,e.g., with reference to FIGS. 7 and 8. Device 1005 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including basestation communications manager 1015, processor 1020, memory 1025,software 1030, transceiver 1035, antenna 1040, network communicationsmanager 1045, and inter-station communications manager 1050. Thesecomponents may be in electronic communication via one or more buses(e.g., bus 1010). Device 1005 may communicate wirelessly with one ormore UEs 115.

Processor 1020 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a central processing unit (CPU), amicrocontroller, an ASIC, an FPGA, a programmable logic device, adiscrete gate or transistor logic component, a discrete hardwarecomponent, or any combination thereof). In some cases, processor 1020may be configured to operate a memory array using a memory controller.In other cases, a memory controller may be integrated into processor1020. Processor 1020 may be configured to execute computer-readableinstructions stored in a memory to perform various functions (e.g.,functions or tasks supporting scrambling sequences for reference signalsduring beam refinement).

Memory 1025 may include random access memory (RAM) and read only memory(ROM). The memory 1025 may store computer-readable, computer-executablesoftware 1030 including instructions that, when executed, cause theprocessor to perform various functions described herein. In some cases,the memory 1025 may contain, among other things, a basic input/outputsystem (BIOS) which may control basic hardware or software operationsuch as the interaction with peripheral components or devices.

Software 1030 may include code to implement aspects of the presentdisclosure, including code to support scrambling sequences for referencesignals during beam refinement. Software 1030 may be stored in anon-transitory computer-readable medium such as system memory or othermemory. In some cases, the software 1030 may not be directly executableby the processor but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

Transceiver 1035 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1035 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1035 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas. In some cases the devicemay have more than one antenna 1040, which may be capable ofconcurrently transmitting or receiving multiple wireless transmissions.

Network communications manager 1045 may manage communications with thecore network 130 (e.g., via one or more wired backhaul links). Forexample, the network communications manager 1045 may manage the transferof data communications for client devices, such as one or more UEs 115.

Inter-station communications manager 1050 may manage communications withother base station 105, and may include a controller or scheduler forcontrolling communications with UEs 115 in cooperation with other basestations 105. For example, the inter-station communications manager 1050may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, inter-station communications manager1050 may provide an X2 interface within an LTE/LTE-A wirelesscommunication network technology to provide communication between basestations 105.

FIG. 11 shows a block diagram 1100 of a wireless device 1105 thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.Wireless device 1105 may be an example of aspects of a UE 115 asdescribed herein. Wireless device 1105 may include receiver 1110, UEcommunications manager 1115, and transmitter 1120. Wireless device 1105may also include a processor. Each of these components may be incommunication with one another (e.g., via one or more buses).

Receiver 1110 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to scramblingsequences for reference signals during beam refinement, etc.).Information may be passed on to other components of the device. Thereceiver 1110 may be an example of aspects of the transceiver 1435described with reference to FIG. 14. The receiver 1110 may utilize asingle antenna or a set of antennas.

UE communications manager 1115 may be an example of aspects of the UEcommunications manager 1415 described with reference to FIG. 14. UEcommunications manager 1115 and/or at least some of its varioussub-components may be implemented in hardware, software executed by aprocessor, firmware, or any combination thereof. If implemented insoftware executed by a processor, the functions of the UE communicationsmanager 1115 and/or at least some of its various sub-components may beexecuted by a general-purpose processor, a DSP, an ASIC, an FPGA orother programmable logic device, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described in the present disclosure.

The UE communications manager 1115 and/or at least some of its varioussub-components may be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations by one or more physical devices. In someexamples, UE communications manager 1115 and/or at least some of itsvarious sub-components may be a separate and distinct component inaccordance with various aspects of the present disclosure. In otherexamples, UE communications manager 1115 and/or at least some of itsvarious sub-components may be combined with one or more other hardwarecomponents, including but not limited to an I/O component, atransceiver, a network server, another computing device, one or moreother components described in the present disclosure, or a combinationthereof in accordance with various aspects of the present disclosure.

UE communications manager 1115 may identify a downlink transmit beam ofa set of downlink transmit beams for synchronization signals transmittedby a base station; transmit a random access message using a first set ofresources, the first set of resources being selected based on theidentified downlink transmit beam; receive, in response to the randomaccess message, one or more downlink beam reference signals scrambledwith respective downlink scrambling sequences of a set of downlinkscrambling sequences, the set of downlink scrambling sequences selectedfrom a set of sets of downlink scrambling sequences based on the firstset of resources; and transmit channel feedback information based onmeasurements of the downlink beam reference signals.

Transmitter 1120 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1120 may be collocatedwith a receiver 1110 in a transceiver module. For example, thetransmitter 1120 may be an example of aspects of the transceiver 1435described with reference to FIG. 14. The transmitter 1120 may utilize asingle antenna or a set of antennas.

FIG. 12 shows a block diagram 1200 of a wireless device 1205 thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure.Wireless device 1205 may be an example of aspects of a wireless device1105 or a UE 115 as described with reference to FIG. 11. Wireless device1205 may include receiver 1210, UE communications manager 1215, andtransmitter 1220. Wireless device 1205 may also include a processor.Each of these components may be in communication with one another (e.g.,via one or more buses).

Receiver 1210 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to scramblingsequences for reference signals during beam refinement, etc.).Information may be passed on to other components of the device. Thereceiver 1210 may be an example of aspects of the transceiver 1435described with reference to FIG. 14. The receiver 1210 may utilize asingle antenna or a set of antennas.

UE communications manager 1215 may be an example of aspects of the UEcommunications manager 1415 described with reference to FIG. 14. UEcommunications manager 1215 may also include synchronization manager1225, PRACH component 1230, reference signal manager 1235, and beammanager 1240.

Synchronization manager 1225 may identify a downlink transmit beam of aset of downlink transmit beams for synchronization signals transmittedby a base station.

PRACH component 1230 may transmit a random access message using a firstset of resources. In some cases, the first set of resources may beselected based on the identified downlink transmit beam. The first setof resources may include time resources, frequency resources, preambleresources, or a combination thereof.

Reference signal manager 1235 may receive, in response to the randomaccess message, one or more downlink beam reference signals scrambledwith respective downlink scrambling sequences of a set of downlinkscrambling sequences, the set of downlink scrambling sequences selectedfrom a set of sets of downlink scrambling sequences based on the firstset of resources. Reference signal manager 1235 may identify a set ofuplink scrambling sequences for one or more candidate uplink beamreference signals from a set of sets of uplink scrambling sequences. Insome cases, reference signal manager 1235 may transmit the one or morecandidate uplink beam reference signals scrambled with respective onesof the set of uplink scrambling sequences. Reference signal manager 1235may identify a second TTI for the receiving of the one or more downlinkbeam reference signals based on a downlink control informationtransmission. In some cases, reference signal manager 1235 may identifytime and frequency resources for the one or more downlink beam referencesignals based on the first set of resources. In some cases, the set ofuplink scrambling sequences is identified based on the first set ofresources or an indicator received in a random access response to therandom access message. In some cases, the second TTI is prior to a firstTTI or subsequent to the first TTI. In some cases, the second TTI andthe first TTI are a same TTI.

Beam manager 1240 may transmit channel feedback information based onmeasurements of the downlink beam reference signals and receive one ormore transmissions from the base station via a downlink beam pairincluding a candidate downlink transmit beam and a candidate downlinkreceive beam, the downlink beam pair selected based on the channelfeedback information.

Transmitter 1220 may transmit signals generated by other components ofthe device. In some examples, the transmitter 1220 may be collocatedwith a receiver 1210 in a transceiver module. For example, thetransmitter 1220 may be an example of aspects of the transceiver 1435described with reference to FIG. 14. The transmitter 1220 may utilize asingle antenna or a set of antennas.

FIG. 13 shows a block diagram 1300 of a UE communications manager 1315that supports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure. The UEcommunications manager 1315 may be an example of aspects of a UEcommunications manager 1415 described with reference to FIGS. 11, 12,and 14. The UE communications manager 1315 may include synchronizationmanager 1320, PRACH component 1325, reference signal manager 1330,access manager 1335, and beam manager 1340. Each of these modules maycommunicate, directly or indirectly, with one another (e.g., via one ormore buses).

Synchronization manager 1320 may identify a downlink transmit beam of aset of downlink transmit beams for synchronization signals transmittedby a base station. For example, synchronization manager 1320 may receivea signal 1345 (e.g., via receiver 1110 or 1210) over one or moredownlink transmit beams and identify one of the downlink transmit beamsfrom the one or more downlink transmit beams based on a measurement(e.g., signal quality or signal strength). Synchronization manager maythen send beam selection information 1350 indicating the identifieddownlink transmit beam to PRACH component 1325.

PRACH component 1325 may transmit a random access message using a firstset of resources. For example, PRACH component 1325 may transmit signal1355 (e.g., via transmitter 1120 or 1220) by encoding bits indicatingthe random access message, identify the first set of resources overwhich the random access message is to be transmitted, and modulate thetransmission over the identified first set of resources. In some cases,the first set of resources may be selected based on the identifieddownlink transmit beam from beam selection information 1350. The firstset of resources may include time resources, frequency resources,preamble resources, or a combination thereof. PRACH component 1325 maysend random access message information 1360 indicating the random accessmessage transmitted in signal 1355 and the first set of resources thatsignal 1355 is transmitted on to reference signal manager 1330.

Reference signal manager 1330 may receive (e.g., in signal 1345 fromreceiver 1110 or 1120), in response to the random access message, one ormore downlink beam reference signals scrambled with respective downlinkscrambling sequences of a set of downlink scrambling sequences, the setof downlink scrambling sequences selected from a set of sets of downlinkscrambling sequences based on the first set of resources. Referencesignal manager 1330 may identify a set of uplink scrambling sequencesfor one or more candidate uplink beam reference signals from a set ofsets of uplink scrambling sequences. In some cases, reference signalmanager 1330 may transmit the one or more candidate uplink beamreference signals scrambled with respective ones of the set of uplinkscrambling sequences. Reference signal manager 1330 may identify asecond TTI for the receiving of the one or more downlink beam referencesignals based on a downlink control information transmission. In somecases, reference signal manager 1330 may identify time and frequencyresources for the one or more downlink beam reference signals based onthe first set of resources (e.g., based on random access messageinformation 1360). In some cases, the set of uplink scrambling sequencesis identified based on the first set of resources (e.g., based on randomaccess message information 1360) or an indicator received in a randomaccess response to the random access message. In some cases, the secondTTI is prior to a first TTI or subsequent to the first TTI. In somecases, the second TTI and the first TTI are a same TTI. Reference signalmanager 1330 may perform measurements on the one or more downlink beamreference signals and send beam measurement information 1365 to beammanager 1340.

Access manager 1335 may receive, in a first TTI, a random accessresponse to the random access message, the random access responseincluding a grant of uplink resources for channel feedback information.For example, access manager 1335 may receive (e.g., via receiver 1110 or1210) a control information signal 1370 and may demodulate and decodethe signal to determine the random access response. In some cases, therandom access response is received within a response window after thetransmission of the random access message. In some cases, the randomaccess response includes an indicator of the second TTI for transmissionof candidate uplink beam reference signals. Access manager 1335 may senduplink resource information 1375 indicating the uplink resourcesdetermined from control information signal 1370 for the channel feedbackinformation to beam manager 1340.

Beam manager 1340 may transmit the channel feedback information based onmeasurements of the downlink beam reference signals. In some cases, thechannel feedback information may be transmitted on the uplink resourcesindicated in uplink resource information 1375. For example, beam manager1340 may transmit signal 1380 (e.g., via transmitter 1120 or 1220) byencoding bits indicating the channel feedback information, identify theuplink resources (e.g., based on uplink resource information 1375) overwhich the channel feedback information is to be transmitted, andmodulate the transmission over the identified uplink resources.Additionally, beam manager 1340 may receive one or more transmissionsfrom the base station via a downlink beam pair including a candidatedownlink transmit beam and a candidate downlink receive beam, thedownlink beam pair selected based on the channel feedback information.

FIG. 14 shows a diagram of a system 1400 including a device 1405 thatsupports scrambling sequences for reference signals during beamrefinement in accordance with aspects of the present disclosure. Device1405 may be an example of or include the components of UE 115 asdescribed above, e.g., with reference to FIG. 1. Device 1405 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including UEcommunications manager 1415, processor 1420, memory 1425, software 1430,transceiver 1435, antenna 1440, and I/O controller 1445. Thesecomponents may be in electronic communication via one or more buses(e.g., bus 1410). Device 1405 may communicate wirelessly with one ormore base stations 105.

Processor 1420 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, processor 1420 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into processor 1420. Processor 1420 may be configured toexecute computer-readable instructions stored in a memory to performvarious functions (e.g., functions or tasks supporting scramblingsequences for reference signals during beam refinement).

Memory 1425 may include RAM and ROM. The memory 1425 may storecomputer-readable, computer-executable software 1430 includinginstructions that, when executed, cause the processor to perform variousfunctions described herein. In some cases, the memory 1425 may contain,among other things, a BIOS which may control basic hardware or softwareoperation such as the interaction with peripheral components or devices.

Software 1430 may include code to implement aspects of the presentdisclosure, including code to support scrambling sequences for referencesignals during beam refinement. Software 1430 may be stored in anon-transitory computer-readable medium such as system memory or othermemory. In some cases, the software 1430 may not be directly executableby the processor but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

Transceiver 1435 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1435 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1435 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1440.However, in some cases the device may have more than one antenna 1440,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

I/O controller 1445 may manage input and output signals for device 1405.I/O controller 1445 may also manage peripherals not integrated intodevice 1405. In some cases, I/O controller 1445 may represent a physicalconnection or port to an external peripheral. In some cases, I/Ocontroller 1445 may utilize an operating system such as iOS®, ANDROID®,MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operatingsystem. In other cases, I/O controller 1445 may represent or interactwith a modem, a keyboard, a mouse, a touchscreen, or a similar device.In some cases, I/O controller 1445 may be implemented as part of aprocessor. In some cases, a user may interact with device 1405 via I/Ocontroller 1445 or via hardware components controlled by I/O controller1445.

FIG. 15 shows a flowchart illustrating a method 1500 for scramblingsequences for reference signals during beam refinement in accordancewith aspects of the present disclosure. The operations of method 1500may be implemented by a base station 105 or its components as describedherein. For example, the operations of method 1500 may be performed by abase station communications manager as described with reference to FIGS.7 through 10. In some examples, a base station 105 may execute a set ofcodes to control the functional elements of the device to perform thefunctions described below. Additionally or alternatively, the basestation 105 may perform aspects of the functions described below usingspecial-purpose hardware.

At block 1505 the base station 105 may receive a first random accessmessage from a first UE over a first set of resources. For example, thebase station 105 may monitor a set of PRACH resources for potentialrandom access messages. The base station 105 may then correlate receivedsignals on the PRACH resources against known preamble sequences toidentify the first random access message. As such, the base station 105may identify time-frequency resources over which the first random accessmessage may be transmitted from the first UE. The base station 105 maythen identify random access messages by correlating and/or demodulatingthe received signals. The operations of block 1505 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of block 1505 may be performed by a PRACH component asdescribed with reference to FIGS. 7 through 10.

At block 1510 the base station 105 may transmit, in a first TTI inresponse to the first random access message, one or more downlink beamreference signals scrambled with respective downlink scramblingsequences of a set of downlink scrambling sequences, the set of downlinkscrambling sequences selected from a plurality of sets of downlinkscrambling sequences based on the first set of resources. For example,the base station 105 may encode bits that indicate the downlink beamreference signals, identify time-frequency resources over which thedownlink beam reference signals are to be transmitted, and modulate thetransmission over the identified time-frequency resources. The basestation 105 may encode separate downlink beam reference signals onrespective downlink beams. As such, the separate downlink beam referencesignals may be transmitted over different or overlapping time-frequencyresources (e.g., beams to different UEs may have reference signalstransmitted on overlapping time-frequency resources but with differentscrambling codes). Additionally, the base station 105 may transmit DCIto indicate the downlink beam reference signals. In some cases, the DCImay be transmitted prior to, concurrently with (e.g., part of), or aftera random access response message transmitted based on the received firstrandom access message. The operations of block 1510 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of block 1510 may be performed by a reference signalmanager as described with reference to FIGS. 7 through 10.

At block 1515 the base station 105 may receive first channel feedbackinformation from the first UE, where the first channel feedbackinformation is based on measurements of the downlink beam referencesignals. For example, the base station 105 may identify time-frequencyresources over which the first channel feedback information may betransmitted from the first UE. The base station 105 may demodulate thetransmission over those time-frequency resources and decode thedemodulated transmission to obtain bits that indicate the first channelfeedback information. The operations of block 1515 may be performedaccording to the methods described herein. In certain examples, aspectsof the operations of block 1515 may be performed by a beam manager asdescribed with reference to FIGS. 7 through 10.

FIG. 16 shows a flowchart illustrating a method 1600 for scramblingsequences for reference signals during beam refinement in accordancewith aspects of the present disclosure. The operations of method 1600may be implemented by a UE 115 or its components as described herein.For example, the operations of method 1600 may be performed by a UEcommunications manager as described with reference to FIGS. 11 through14. In some examples, a UE 115 may execute a set of codes to control thefunctional elements of the device to perform the functions describedbelow. Additionally or alternatively, the UE 115 may perform aspects ofthe functions described below using special-purpose hardware.

At block 1605 the UE 115 may identify a downlink transmit beam of aplurality of downlink transmit beams for synchronization signalstransmitted by a base station. For example, the UE 115 may identify thedownlink transmit beam for synchronization signals transmitted by thebase station based on a synchronization period. In some cases, the basestation may transmit the synchronization signals sequentially (e.g., ina beamswept fashion) or simultaneously. The operations of block 1605 maybe performed according to the methods described herein. In certainexamples, aspects of the operations of block 1605 may be performed by asynchronization manager as described with reference to FIGS. 11 through14.

At block 1610 the UE 115 may transmit a random access message using afirst set of resources. In some cases, the first set of resources may beselected based on the identified downlink transmit beam. For example,the UE 115 may identify the first set of resources, encode bits thatindicate the random access message on the first set of resources, andmodulate the random access message over the identified first set ofresources. In some cases, the first set of resources may be contentionor contention-free resources. For example, the base station may indicatethe first set of resources (e.g., in an uplink grant or DCI) for the UE115 to transmit the random access message. Alternatively, the UE 115 maytransmit the random access message without receiving an uplink grant.The operations of block 1610 may be performed according to the methodsdescribed herein. In certain examples, aspects of the operations ofblock 1610 may be performed by a PRACH component as described withreference to FIGS. 11 through 14.

At block 1615 the UE 115 may receive, in response to the random accessmessage, one or more downlink beam reference signals scrambled withrespective downlink scrambling sequences of a set of downlink scramblingsequences, the set of downlink scrambling sequences selected from aplurality of sets of downlink scrambling sequences based on the firstset of resources. For example, the UE 115 may identify time-frequencyresources over which the downlink beam reference signals may betransmitted from a base station 105 serving the cell. The UE 115 maydemodulate and descramble the transmission over those time-frequencyresources and determine if the downlink beam reference signals weretransmitted using one or more of the selected set of downlink scramblingsequences. The operations of block 1615 may be performed according tothe methods described herein. In certain examples, aspects of theoperations of block 1615 may be performed by a reference signal manageras described with reference to FIGS. 11 through 14.

At block 1620 the UE 115 may transmit channel feedback information basedon measurements of the downlink beam reference signals. For example, theUE 115 may encode the channel feedback information, identifytime-frequency resources over which the channel feedback information isto be transmitted, and modulate the channel feedback information overthe identified time-frequency resources. The operations of block 1620may be performed according to the methods described herein. In certainexamples, aspects of the operations of block 1620 may be performed by abeam manager as described with reference to FIGS. 11 through 14.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.The terms “system” and “network” are often used interchangeably. A codedivision multiple access (CDMA) system may implement a radio technologysuch as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc.CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releasesmay be commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE and LTE-A are releases of UMTSthat use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, NR, and GSM aredescribed in documents from the organization named “3rd GenerationPartnership Project” (3GPP). CDMA2000 and UMB are described in documentsfrom an organization named “3rd Generation Partnership Project 2”(3GPP2). The techniques described herein may be used for the systems andradio technologies mentioned above as well as other systems and radiotechnologies. While aspects of an LTE or an NR system may be describedfor purposes of example, and LTE or NR terminology may be used in muchof the description, the techniques described herein are applicablebeyond LTE or NR applications.

In LTE/LTE-A networks, including such networks described herein, theterm evolved node B (eNB) may be generally used to describe the basestations. The wireless communications system or systems described hereinmay include a heterogeneous LTE/LTE-A or NR network in which differenttypes of eNBs provide coverage for various geographical regions. Forexample, each eNB, next generation NodeB (gNB), or base station mayprovide communication coverage for a macro cell, a small cell, or othertypes of cell. The term “cell” may be used to describe a base station, acarrier or component carrier associated with a base station, or acoverage area (e.g., sector, etc.) of a carrier or base station,depending on context.

Base stations may include or may be referred to by those skilled in theart as a base transceiver station, a radio base station, an accesspoint, a radio transceiver, a NodeB, eNodeB (eNB), gNB, Home NodeB, aHome eNodeB, or some other suitable terminology. The geographic coveragearea for a base station may be divided into sectors making up only aportion of the coverage area. The wireless communications system orsystems described herein may include base stations of different types(e.g., macro or small cell base stations). The UEs described herein maybe able to communicate with various types of base stations and networkequipment including macro eNBs, small cell eNBs, gNBs, relay basestations, and the like. There may be overlapping geographic coverageareas for different technologies.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell is alower-powered base station, as compared with a macro cell, that mayoperate in the same or different (e.g., licensed, unlicensed, etc.)frequency bands as macro cells. Small cells may include pico cells,femto cells, and micro cells according to various examples. A pico cell,for example, may cover a small geographic area and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A femto cell may also cover a small geographic area (e.g., ahome) and may provide restricted access by UEs having an associationwith the femto cell (e.g., UEs in a closed subscriber group (CSG), UEsfor users in the home, and the like). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a small cell may be referred toas a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB maysupport one or multiple (e.g., two, three, four, and the like) cells(e.g., component carriers).

The wireless communications system or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations may have similar frame timing, andtransmissions from different base stations may be approximately alignedin time. For asynchronous operation, the base stations may havedifferent frame timing, and transmissions from different base stationsmay not be aligned in time. The techniques described herein may be usedfor either synchronous or asynchronous operations.

The downlink transmissions described herein may also be called forwardlink transmissions while the uplink transmissions may also be calledreverse link transmissions. Each communication link describedherein—including, for example, wireless communications system 100 and200 of FIGS. 1 and 2—may include one or more carriers, where eachcarrier may be a signal made up of multiple sub-carriers (e.g., waveformsignals of different frequencies).

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of at least one of A, B, or C meansA or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, asused herein, the phrase “based on” shall not be construed as a referenceto a closed set of conditions. For example, an exemplary step that isdescribed as “based on condition A” may be based on both a condition Aand a condition B without departing from the scope of the presentdisclosure. In other words, as used herein, the phrase “based on” shallbe construed in the same manner as the phrase “based at least in parton.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude RAM, ROM, electrically erasable programmable read only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or wireless technologies such as infrared, radio, and microwave,then the coaxial cable, fiber optic cable, twisted pair, DSL, orwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include CD, laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

1. (canceled)
 2. A method for wireless communication, comprising:transmitting, to a base station, a random access message using a firstset of resources; receiving, in response to the random access message,one or more downlink reference signals of a plurality of downlinkreference signals transmitted by the base station, the plurality ofdownlink reference signals scrambled with respective downlink scramblingsequences of a set of downlink scrambling sequences, the set of downlinkscrambling sequences selected from a plurality of sets of downlinkscrambling sequences based at least in part on the first set ofresources; and transmitting channel feedback information based at leastin part on measurements of the one or more downlink reference signals.3. The method of claim 2, further comprising: receiving one or moretransmissions from the base station via a downlink beam pair comprisinga downlink transmit beam and a downlink receive beam, the downlink beampair selected based at least in part on the channel feedbackinformation.
 4. The method of claim 2, further comprising: identifying aset of uplink scrambling sequences for one or more uplink referencesignals from a plurality of sets of uplink scrambling sequences; andtransmitting the one or more uplink reference signals scrambled withrespective ones of the set of uplink scrambling sequences.
 5. The methodof claim 4, wherein the set of uplink scrambling sequences is identifiedbased at least in part on the first set of resources, an indicatorreceived in a random access response to the random access message, or asecond indicator received in a handover command.
 6. The method of claim2, further comprising: receiving, in a first transmission time interval,a random access response to the random access message, the random accessresponse comprising a grant of uplink resources for the channel feedbackinformation.
 7. The method of claim 6, wherein the random accessresponse is received within a response window after the transmission ofthe random access message.
 8. The method of claim 6, further comprising:identifying a second transmission time interval for the receiving of theone or more downlink reference signals based at least in part on adownlink control information transmission.
 9. The method of claim 8,wherein the second transmission time interval is prior to the firsttransmission time interval or subsequent to the first transmission timeinterval.
 10. The method of claim 8, wherein the second transmissiontime interval and the first transmission time interval are a sametransmission time interval.
 11. The method of claim 6, wherein therandom access response comprises an indicator of a second transmissiontime interval for transmission of uplink reference signals.
 12. Themethod of claim 2, wherein the first set of resources comprise timeresources, frequency resources, preamble resources, or a combinationthereof.
 13. The method of claim 2, wherein time and frequency resourcesfor the one or more downlink reference signals are based at least inpart on the first set of resources.
 14. The method of claim 2, furthercomprising: identifying a downlink transmit beam of a plurality ofdownlink transmit beams for synchronization signals transmitted by thebase station; and selecting the first set of resources based at least inpart on the identified downlink transmit beam.
 15. A method for wirelesscommunication, comprising: transmitting, to a base station, a randomaccess message using a first set of resources; receiving, from the basestation and within a random access response window after transmittingthe random access message, a random access response message and one ormore downlink reference signals of a plurality of downlink referencesignals transmitted by the base station, wherein the one or moredownlink reference signals are received based at least in part on thefirst set of resources; and transmitting channel feedback informationbased at least in part on measurements of the one or more downlinkreference signals.
 16. The method of claim 15, wherein receiving therandom access response message and the one or more downlink referencesignals comprises: receiving the random access response message in afirst time interval of the random access response window; and receivingthe one or more downlink reference signals in a second time interval ofthe random access response window, the second time interval beingdifferent than the first time interval.
 17. The method of claim 15,wherein receiving the random access response message and the one or moredownlink reference signals comprises: receiving the random accessresponse message and the one or more downlink reference signals in asame time interval of the random access response window.
 18. The methodof claim 15, further comprising: receiving downlink control informationin a control region of a time interval of the random access responsewindow, the downlink control information indicating a presence of theone or more downlink reference signals within the random access responsewindow.
 19. The method of claim 18, wherein receiving the downlinkcontrol information comprises: receiving the downlink controlinformation in a common search space in the control region of the timeinterval.
 20. The method of claim 18, wherein receiving the one or moredownlink reference signals comprises: receiving the one or more downlinkreference signals in a data region of the time interval of the randomaccess response window.
 21. The method of claim 18, wherein receivingthe one or more downlink reference signals comprises: receiving the oneor more downlink reference signals in a data region of an additionaltime interval of the random access response window, the additional timeinterval occurring subsequent to the time interval.
 22. The method ofclaim 18, further comprising: receiving an additional downlink controlinformation in the control region of the time interval of the randomaccess response window, the additional downlink control informationindicating a presence of the random access response message in a dataregion of the time interval of the random access response window. 23.The method of claim 18, wherein the downlink control informationindicates a presence of the random access response message in a dataregion of the time interval of the random access response window. 24.The method of claim 18, wherein the downlink control information isscrambled with an identifier associated with the random access responsemessage.
 25. The method of claim 15, wherein the plurality of downlinkreference signals are scrambled with respective downlink scramblingsequences of a set of downlink scrambling sequences, the set of downlinkscrambling sequences selected from a plurality of sets of downlinkscrambling sequences based at least in part on the first set ofresources.
 26. A method for wireless communication, comprising:transmitting, to a base station, a random access message using a firstset of resources; receiving, from the base station, a random accessresponse message based at least in part on transmitting the randomaccess message; and transmitting, to the base station in response to therandom access response message, one or more uplink reference signals,the one or more uplink reference signals scrambled with respectiveuplink scrambling sequences of a set of uplink scrambling sequences. 27.The method of claim 26, wherein the set of uplink scrambling sequencesis identified based at least in part on the first set of resources, anindicator received in the random access response message, or a secondindicator received in a handover command.
 28. The method of claim 26,further comprising: transmitting, to the base station in response to therandom access response message, an access report comprising anindication of a selected downlink transmit beam for subsequentcommunications with the base station, the report transmitted based atleast in part on a grant received with the random access responsemessage.
 29. The method of claim 28, wherein the access report and theone or more uplink reference signals are transmitted within a same timeinterval.
 30. The method of claim 28, wherein the access report and theone or more uplink reference signals are transmitted within differenttime intervals.
 31. A method for wireless communication at a basestation, comprising: receiving, from a user equipment (UE), a randomaccess message using a first set of resources; transmitting, in responseto the random access message, one or more downlink reference signals ofa plurality of downlink reference signals transmitted by the basestation, the plurality of downlink reference signals scrambled withrespective downlink scrambling sequences of a set of downlink scramblingsequences, the set of downlink scrambling sequences selected from aplurality of sets of downlink scrambling sequences based at least inpart on the first set of resources; and receiving channel feedbackinformation based at least in part on measurements of the one or moredownlink reference signals.